Method of grease manufacture



O :t.28,1 6 9 W 'ETAL 3,475,337

METHOD OF GREASE MANUFACTURE Original Filed Dec. 24, 1963 United States Patent U.S. Cl. 25241 12 Claims ABSTRACT OF THE DISCLGSURE An improved method for the preparation of a sodium soap thickened lubricating grease comprising the steps of saponification, dehydration and soap conditioning, and cooling with oil addition, wherein the dehydration and soap conditioning steps are carried out on a grease mixture containing 45% by weight of soap at a temperature of from about F. below the soap melting point up to just below the melting point while shearing a withdrawn portion of the grease mixture by passing it through a shear valve having a pressure drop of 20-100 pounds per square inch across same and returning the sheared withdrawn portion to the balance of the grease mixture.

This invention relates to an improved method for making sodium soap thickened greases, and more particularly to an improved method for making such greases in a continuous manner.

Sodium soap thicken-ed greases are conventionally prepared by the method comprising saponifying a saponifiable material in a portion of the lubricating oil employed in the grease, dehydrating the grease mixture obtained and heating it for a further period in a soap conditioning step at a temperature below the melting point of the soap, and thereafter cooling with the addition of the remainder of the lubricating oil employed in the grease at a lower temperature. The preparation of sodium soap thickened greases by this so-called low temperature method involves a special difiicultly arising from the tendency of the soap fibers to agglomerate strongly during their formation in the saponification and dehydration steps. The process therefore requires a lengthy soap conditioning step, which is ordinarily carried out at temperature in the range from about 270 F. to about 330 F., to convert the grease mixture into a form which will accept additional lubricating oil, ordinarily requiring at least about two hours after the dehydration is substantially completed. It is also necessary in carrying out the preparation under the conventional conditions to add the remainder of the lubricating oil at a very slow rate in order to obtain a satisfactorily smooth product. For these reasons, the process has the disadvantage of requiring very long manufacturing lines,

about 21 hours being required in a typical preparation carried out in a conventional grease kettle.

Recently, it has been found, as disclosed by C. L. Dowden, Jr., W. R. Coons, I r. and H. I. Pitman in their copending application Ser. No. 282,340, filed May 22, 1963, now Patent No. 3,242,987, that the time required for these preparations can be greatly shortened, down to as low as about 3 hours total manufacturing time, by a method which comprises shearing the grease mixture at an elevated temperature during the oil addition step. However, attempts to obtain further reductions in the manufacturing time have resulted in unsatisfactory products, due to lumpiness and particularly to very inferior shear stability.

The present invention overcomes the above difiiculties of the prior art methods and provides a means of obtaining sodium soap thickened greases of very satisfactory Patented Oct. 28, 1Q69 properties, including shear stability, in greatly shortened manufacturing times. The method of our invention comprises essentially saponification, dehydration, soap conditioning and cooling steps wherein the dehydration and soap conditioning steps are carried out in a substantially simultaneous operation at a temperature within a range which is substantially higher than the temperature range ordinarily employed in the soap conditioning step in the preparation of sodium soap thickened greases by low temperature methods of the prior art, and with continuous shearing of the grease mixture during the dehydration and soap conditioning steps by recycling it through a shear valve at a rapid rate. The process also preferably comprises shearing the grease mixture during the cooling at a temperature below about 250 F., the amount of shearing in this manner and the soap concentration of the grease mixture in the dehydration and soap conditioning steps being critical features for obtaining high yields in the process carried out in accordance with our invention.

While the method of our invention may be employed very advantageously in the preparation of sodium soap thickened greases by various methods including conventional grease kettle preparations, it is employed with special advantage in the preparation of such greases in continuous processes, wherein it is particularly difficult to obtain sodium soap thickened greases of satisfactory quality. The process comprising the preferred embodiment of our invention is carried out as described by J. H. Greene, W. R. Hencke, C. L. Dowden, Jr. and H. J. Pitman in their copending, cofiled application Ser. No. 333,- 164 of Dec. 24, 1963, and now abandoned, employing the conditions disclosed hereinbelow for obtaining products of good shear stability and other satisfactory properties in greatly shortened manufacturing times, resulting in commercially feasible high throughput rates for an operation of this type.

The accompanying drawing is a diagrammatic illustration of one form of apparatus suitable for making greases in accordance with the preferred embodiment of our invention.

Referring to the drawing, 1 is a tubular reactor in the form of a coil, situated inside chamber 2 and connected with lines 6 and 7. Chamber 2 is sealed by flange 3 and provided with inlet line 4 and outlet line 5 for steam or other heating fluid. Vessel 15 contains saponifiable material, or a mixture of saponifiable material and lubricating oil, which is maintained at a temperature above the melting point of the saponifiable material by heating means 16. Ordinarily, vessel 15 will contain a mxiture of saponifiable material and lubricating oil comprising from about 10 percent to about percent by weight of the mixture. Vessel 20 contains a water solution or oil slurry of a sodium base such as sodium hydroxide or sodium carbonate. It preferably contains an aqueous solution of sodium hydroxide, comprising at least sufiicient water to completely dissolve the sodium hydroxide.

In carrying out the grease making process, the saponifiable material passes at a controlled rate through line 17, containing valve 18 and pump 19, into line 24, while a solution or slurry of the metal base passes from tank 20 at a controlled rate through line 21, containing valve 22 and pump 23, into line 24. From line 24 the mixture of saponifiable material and metal base passes through line 25 into line 7 at the intake of pump 10, and from pump 10 it passes through line 6 into zone 1. When the saponification is carried out employing. a slurry of the metal base in oil, it is generally desirable to introduce a small amount of water or steam into the reaction zone in order to promote the reaction. The reaction mixture in reaction zone 1 is maintained under superatmospheric pressure at least sufficient to maintain the water present or produced in the reaction in the liquid phase, and at an elevated temperature suflicient to obtain a rapid reaction between the metal base and the saponifiable material. The reaction zone is very suitably operated under a pressure of about 100 to about 200 pounds per square inch gauge and a temperature of about 300350 F. It is preferably operated at a pressure of about 120-170 pounds per square inch gauge and a temperature in th range from about 320 F. to about 340 F.

The reactant stream is passed through reaction zone 1 at a velocity Which is preferably sufficient to maintain turbulent flow within the zone. With special advantag the reactant stream may be passed through the reaction zone at a velocity resulting in highly turbulent flow, preferably at a velocity resulting in a Reynolds number in the range from about 4000 to about 100,000. Flow rates .required to obtain the desired degree of turbulence are generally within the range from about 0.6 to about 12.0 cubic feet per minute per square inch of reactor cross-section. In the process comprising the preferred embodiment of this invention, the saponification mixture is recycled continuously through reactor 1 by way of lines 6 and 7 and pump 10, as a means of obtaining a sufliciently high rate of flow of the reactant stream through the saponification zone. The recycle rate employed is ordinarily in a ratio from about 10:1 to about 100:1 with the rate of throughput, although somewhat lower or higher recycling ratios may be employed in some cases, such as a recycle ratio as low as about 1:1 and as high as about 200:1.

A product stream from reaction zone 1 passes to dehydration zone 30 by way of line 7 and line 26 containing valve 27. Dehydration zone 30 is an upright zone of relatively large diameter as compared with zone 1, sealed by flange 31 and provided with line 32 which is connected to a pressure regulator means (not shown), It may be jacketed or otherwise provided with indirect heating or cooling means. The grease mixture in zone 30 is maintained at an elevated temperature in the range from about F. below the melting point of the soap up to just below the melting point of the soap, and at a pressure substantially lower than that in reaction zone 1, very suitably under a partial vacuum from about 5 to about 25 inches of mercury. In the preparation of sodium soap thickened greases from saponifiable materials comprising chiefly C1648 fatty acid materials such as sodium stearate and sodium tallowate greases, the grease mixture within zone is preferably maintained at a temperature in the range from about 350 F. to about 370 F., most advantageously at a temperature in the range from about 360 F. to about 370 F., and under a partial vacuum from about 15 to about 25 inches of mercury.

During its residence in zone 30, the grease mixture is recycled continuously through line 33, containing pump 34 and valves 35 and 37. Valve 37 is a shear valve, suitably a gate valve, set in a partially closed position so as to give a pressure drop of about 20-100 pounds per square inch, and preferably about 30-80 pounds per square inch, across the valve. The recycling is preferably carried out at a rate such that the volume of recycled grease mixture is equal to the total average volume of grease mixture within zone 30 (l batch turnover) within one minute, and providing at least about 5 batch turnovers during the average residence time of the grease mixture within the zone. The residence time of the grease mixture in zone 30 will ordinarily be from about 5 minuates to about 1 hour, although somewhat longer or shorter periods may be employed in some cases. In some cases, the operation may be carried out with a residence time of the grease mixture in zone 30 only suflicient t0 dehydrate the grease mixture to a suitably low water content. Ordinarily, the residence time of the grease mixture in zone 30 includes a period of at least about 10 minutes, and preferably from about 15 to about 30 minutes, after the dehydration is substantially complete.

Additional lubricating oil from tank 40 may be added to the grease mixture at various steps in the process in order to obtain the desired soap concentration or to assist in heating or cooling the grease mixture. Such additional oil may pass into the grease mixture in line 26 by Way of line 41, containing valve 42, line 43 containing pump 44 and valve 45', and line 49 containing valve 50. Additional lubricating oil is added very advantageously in this manner so as to provide at least about 10 percent of lubricating oil in the grease mixture in line 26 when the saponification is carried out with no lubricating oil or only a very small arnout of lubricating oil present in the saponification mixture. The oil added in this manner is preferably preheated by passing through heater 46 by way of line 43a containing valve 4511. Additionally or alternatively, lubricating oil from tank 40 may pass into the saponification mixture in zone 1 by passing from line 43 to line 47 containing valve 48 and into line 25. Oil added in this manner is employed either in addition to or in place of lubricating oil employed in admixture with the saponification material in tank 15. It is preferably preheated in heater 46, very suitably to a temperature in about the range ISO-350 F.

Additionally or alternatively to the lubricating oil addition in the above manner, lubricating oil may be added from tank 40 to the grease mixture during the dehydration and soap conditioning steps. The oil added at this stage of the process may pass into the grease mixture in zone 30 through line 51, containing valve 52. With special advantage in some cases, it may pass through line 53, containing valve 54, into the recycle stream of grease mixture in line 33 as a means of aiding in the recycling when a heavy grease mixture is being circulated, and also as a means of increasing the rate of dehydration by increasing the temperature of the recycle stream in some cases. Additional oil is added in the above manner as required to provide a grease mixture in zone 30 containing about -85 percent by weight of lubricating oil, and preferably about -80 percent by weight of lubricating oil.

Indirect heating or cooling of the grease mixture in zone 30 may be employed either in addition or alternatively to the heating or cooling by oil addition as clescribed above. The indirect heating or cooling may be obtained very conveniently by employing a jacketed vessel for zone 30 and passing a heat exchange fluid through the vessel jacket. Very advantageously in some cases, indirect heating or cooling is applied to the recycle stream of grease mixture in line 33 by passing the grease mixture through heat exchanger 36 by way of line 33a, containing valve 350. It is, for example, particularly advantageous in some cases to cool the recycle stream in this manner in order to obtain an increased effect by the shearing, due to the more viscous grease mixture obtained by the cooling, while the temperature of this grease mixture in zone 30 is maintained at a higher temperature within the preferred soap conditioning temperature range as disclosed above.

A stream of substantially dehydrated grease mixture is continuously withdrawn from the recycle stream in line 33 by way of line 75 containing pump '76. Additional lubricating oil at a lower temperature is added to the grease mixture in line 75 from tank 60 by way of line 61 containing valve 62, pump 67 and line 66 containing valves 68 and 69. It is ordinarily preferable to add this oil at a temperature substantially lower than that of the grease mixture, very suitably in some cases at ambient temperature. However, in many cases, it is advantageous to preheat this oil, very suitably to a temperature in about the range 150-250" F., by passing it through heat exchanger 70 by way of line 6611, containing valve 68a, particularly where a high rate of oil addition is employed or where it is desirable to employ a slower cooling rate. Alternatively or additionally, oil may be introduced into line from tank 40 by way of line 41, line 64, containing valve 65, and line 66. Tanks 40 and 60 are generally employed in conjunction in the process only when two different lubricating oils are employed in the grease.

From line 75, the grease mixture passes into line 79,

containing pump 80 and valves 81 and 83. Valve 81 is a shear valve, such as a gate valve, which is operated with a substantial pressure drop. Where it is desirable to obtain additional cooling, the grease mixture may pass through cooler 85 by way of line 79a, containing valve 83a. The process is preferably carried out with recycling of the grease mixture through line 79 by way of line 89 in order to obtain multiple passes through shearing valve 81 as well as cooler 85 in some cases. From line 79 a stream of the grease mixture is taken off through line 87 containing valve 88. Additional lubricating oil may be added to this stream of grease mixture by way of line 71, containing valve 72, such additional oil being mixed with the grease mixture as the combined stream passes through valve 88, which is operated as a shear valve. The stream of grease mixture containing oil added in this manner may pass through additional shearing means if desired. The additional lubricating oil added to the grease mixture during the cooling, including that added to the grease mixture in line 75 and in line 87, preferably amounts to at least about 50 percent of the total oil contained in the grease, 'and very advantageously, about 6090 percent of the total oil contained in the finished grease.

Any additives employed in the grease are preferably introduced into the grease mixture during the cooling, ordinarily when the grease mixture is below about 250 F. As shown in the diagram, the additives may be added from tank 90 by way of line 91, containing valve 92 and pump 93, into the grease mixture in line 75 after the addition of lubricating oil from line'66. When the grease mixture at this point is not at a suitably low temperature, the additives may be added at some later point in the cooling and finishing section.

It is ordinarily advantageous to recycle the grease mixture through shearing valve 81 operated with a pressure drop in about the range 75200 pounds per square inch gauge and preferably about 100-180 pounds per square inch gauge, employing a recycle ratio from about 1:1 to about 100:1, and preferably from about 5:1 to about 50:1. Shearing in this manner is preferably carried out upon the grease mixture at a temperature in about the range 180240 F.

Suitable saponifiable materials for use in this grease preparation compirse higher fatty acids containing from about '12 to 32 carbon atoms per molecule, their glycerides and other esters, and mixtures thereof. Particularly suitable saponifiable materials are those wherein the fatty acids comprise at least a major proportion of C fatty acids and the glycerides of such acids. A particularly suitable saponifiable material is tallow, containing about 1-10 percent of free fatty acids and having an iodine number from about 40 to 80.

The oleaginous liquids employed in these greases may be any suitable oils having lubricating characteristics, including the conventional mineral lubricating oils, synthetic oils obtained by various refining processes such as cracking and polymerization and other synthetic oleaginous compounds such as high molecular weight ethers and esters. The dicarboxylic acid esters, such as di-2F ethylhexyl sebacate, di(secondary amyl) sebacate, di-2- ethylhexyl azelate, di-iso-octyl adipate, etc., comprise a particularly suitable class of synthetic oils and may be employed either as the sole oleaginous component of the grease or in combination with other synthetic oils or mineral oils. Suitable mineral oils for use in these greases are those having viscosities in the range from about 100 to about 8,000 seconds Saybolt Universal at 100 F., which may be'blends of high and low viscosity oils. They may be either naphthenic or parafiinic in type, or blends of two or more oils of these different types.

In the preparation of greases from synthetic oils which are hydrolyzed under the saponification conditions, the saponification is preferably carried out in the absence of any lubricating oil or of a minor amount of lubricating oil which is substantially inert under the saponification conditions, such as a mineral oil, and the synthetic oil added at later stages to the grease making process as described hereinabove.

The following example is illustrative of grease preparations carried out in accordance with this invention.

EXAMPLE I A sodium tallowate grease was prepared by the method of this invention as described below.

The apparatus employed in the preparation comprised a coil reactor, a dehydrator and a cooler with auxiliary equipment for circulating the grease mixture through each of these zones as shown in the figure, as well as for introducing reactants and additional lubricating oil, circulating the grease mixture between the zones and withdrawing a product stream. The reactor consisted of a 21 foot section of inch Schedule 40 black iron pipe (0.824 inch inside diameter) formed into a coil having a 4 inch inside diameter and mounted in a 3 foot section of 12 inch pipe serving as a steam chamber. The recycle line on the reaction zone comprised 9 feet of 4 inch pipe containing a recycle pump, which was a Viking Rotary heavy duty pump having a capacity of 18 gallons per minute at 1200 revolutions per minute. The capacity of the reactor and recycle line including the pump was 0.12 cubic feet. The dehydrator comprised a 3 foot section of 10 inch Schedule 40 black iron pipe with a blind flange and a bell cap on the ends and electrically heated by a wrapping of resistance Wire on the outside. The recycle line on the dehydrator consisted of a 5 foot section of 0.824 inch in side diameter pipe containing a recycle pump of the same type as that employed in the recycle line on the reactor and a Fulflo valve. The dehydrator was connected at the top by a 2.067 inch inside diameter pipe to a vacuum jet with a condenser. The reactor and dehydrator were connected by a 0.824 inch inside diameter pipe containing a Fulflo valve.

The following materials were employed in the preparation: The saponifiable material employed was a commercial high acid hard tallow. Typical tests upon this material include a saponification number of 200, a free fatty acid content of 4.2 percent, an iodine number of 52 and a titer of 41.6 C. The lubricating oil employed was a deasphalted and dewaxed residuum from a paraffin base crude having a Saybolt Universal viscosity at 210 F. of about 189 seconds. The saponifying agent was sodium hydroxide in the form of a 49 percent aqueous solution.

Following is a detailed description of the method employed in the preparation. Streams of saponifiable material and lubricating oil preheated to 210 F. were charged to the saponification zone at rates of 0.296 pound per minute and 0.557 pound per minute, respectively, while the alkali solution at room temperature was charged at 0.086 pound per minute. The reaction mixture was heated in the reactor to 333 F. under a pressure of 155 pounds per square inch (coil inlet) to pounds per square inch (coil outlet). Recycling on the reactor was carried out at a rate of 18 gallons per minute, resulting in a recycle ratio of 144:1. The product stream, having a calculated soap content of 30.8 percent, was introduced into the dehydrator where it was maintained at 364 F. and under a vacuum of 20 inches of mercury while it was recycled at a rate of 18 gallons per minute through the recycle line with the shear valve set to give a pressure drop of about 10 pounds per square inch. No additional oil was added to the grease mixture in the dehydrator in this preparation.

The level of. the grease mixture in the dehydrator was maintained at about 15 inches, resulting in an average residence time of the grease mixture of 49.4- minutes, during which time the grease mixture was subjected to 144 passes through the recycle line.

The dehydrated product stream was withdrawn from the dehydrator at a rate of 0.895 pound per minute and passed to the finishing section where it was cooled by the addition of lubricating oil at 190 F. at a rate of 4.150 pounds per minute. The combined stream was recycled through the shear valve at a rate of 10 gallons per minute, resulting in a recycle ratio of 14.821 and a total time of the grease mixture in the finishing section of 0.44 minute. Recycling through the cooler was not employed in this preparation. The shear valve in the recycle line was set to give a pressure drop of 140 pounds per square inch. The product stream Withdrawn from the finishing section was at 195 F. The total average time required in the grease preparation was about 1 hour.

A grease having the smooth, slightly stringy texture desired in a sodium base grease of this type and superior lubricating properties was obtained as described above.

The following analyses and tests were obtained upon this product:

Composition, percent:

Sodium soap 5.3 Free neutral fat 0.23 Free fatty acids 0.17 Free alkali None Water 0.05 Tests:

Dropping Point, ASTM, F. 306 Penetration, ASTM at 77:

Unworked 355 Worked, 60 strokes 383 Worked, 100,000 strokes 382 Shell Roll Test: Penetration point change +12 The above data show that a sodium tallowate grease of excellent lubricating properties, including high shear stability, was obtained in an excellent yield and in a greatly shortened manufacturing time by the method of our invention. In contrast to these results, a grease prepared in substantially the same manner except that the dehydration and soap conditioning steps were carried out at 300 F., was unsatisfactory from the standpoint of shear stability, giving a penetration change of 140 points in the Shell Roll Test. In addition, very substantially lower yields were obtained by carrying out this preparation with more dilute grease mixtures in the soap conditioning step and also with the finishing step carried out employing less severe shearing, over 1 percent additional soap being required to produce a grease of the same grade when the shear valve in the finishing section was operated with a pressure drop of 60 pounds per square inch gauge.

Obviously, many modifications and variations of the invention as heretofore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the preparation of a sodium soap thickened lubricating grease by a method which comprises saponifying a saponifiable fatty acid material with a sodium base in the presence of a portion of the lubricating oil contained in the finished grease and of a minor amount of water, further heating the resulting grease mixture in dehydration and soap conditioning steps under pressure substantially less than in the saponification step and thereafter cooling and adding the remainder of the lubricating oil contained in the grease, the improvement resulting in a greatly shortened manufacturing time required for producing a grease of satisfactory lubricating properties, which comprises carrying out the soap conditioning step and the dehydration step upon the grease mixture comprising about 15-45% by weight of soap at a temperature for the soap conditioning step in the range from about F. below the melting point of the soap to just below the melting point of the soap substantially simultaneously while subjecting the grease mixture to shearing by continuously withdrawing a minor stream of grease mixture from a maintained body of the said mixture,

passing the said stream thru a shear valve with a pressure drop of about 20-100 pounds per square inch across said valve and returning the said stream to the said maintained body of grease mixture.

2. The process of claim 1 wherein the said grease mixture is recycled at a rate such that the volume of recycled grease mixture equals the total average amount of grease mixture in the said maintained body within about 1 minute, and providing a total volume of recycled grease mixture equal to at least about 5 times the total average volume of grease mixture in the said maintained body during the average residence time of the grease mixture within the said maintained body.

3. The process of claim 1 wherein the said dehydration and soap conditioning steps are carried out within a period from about 5 minutes to about 1 hour.

4. The process of claim 1 wherein said cooling step is carried out with shearing of the grease mixture at a temperature in about the range 180-240 F. by recycling the grease mixture through a shear valve with a pressure drop of about 75-200 pounds per square inch gauge.

5. The process of claim 1 wherein said lubricating oil is a mineral lubricating oil.

6. The process of claim 1 wherein the said saponifiable material comprises at least a major proportion of fatty acid materials selected from the class consisting of C fatty acids, their glycerides and mixtures thereof.

7. The process of claim 1 wherein the said saponifiable material is tallow, having an Iodine Number in about the range 40-80 and comprising about l-lO percent of free fatty acids.

8. A continuous process for manufacturing a lubricating grease which comprises continuously introducing a reaction mixture consisting essentially of a saponifiable material and a sodium base together with minor amounts of water and lubricating oil into a reaction zone wherein the said mixture is maintained at a temperature in about the range 300-350 F. and under a pressure of about -200 pounds per square inch for a period sufficient to obtain at least substantially complete reaction, continuously withdrawing a grease mixture comprising sodium soap and lubricating oil from said reaction zone, introducing the said grease mixture into a dehydration zone and adding any additional lubricating oil required to give a grease mixture containing about 55-85 percent of lubricating oil, maintaining the said grease mixture in the said dehydration zone at an elevated temperature in the range from just below the melting point of the said soa to about 25 F. below the melting point of the soap and under a lower pressure than the said reaction zone for a period from about 15 minutes to about 1 hour, including at least about 10 minutes after dehydration of the grease mixture is substantially complete, and thereafter withdrawing a dehydrated stream of the said grease mixture and cooling it with the addition of the remainder of the lubricating oil employed in the said grease at a substantially lower temperature than the said grease mixture, the said grease mixture in the said dehydration zone being subjected to a shearing operation which is carried out by continuously withdrawing a minor stream of grease mixture from a maintained body thereof and recycling the said stream to the said dehydration zone at a point above the said body of grease mixture through a recycle line containing a shear valve operated with a pressure drop across the said valve of about 20-100 pounds per square inch, at a rate such that the volume of recycled grease mixture equals the average volume of grease mixture Within the said zone within about 1 minute and the total volume of recycled grease mixture during the average residence time of the grease mixture within the said zone equals at least about 5 times the average volume of grease mixture within the said zone.

9. The process of claim 8 wherein the said reaction mixture is passed through a tubular reaction zone at a velocity sufiicient to maintain turbulent flow character- 9 ized by a Reynolds Number of from about 4000 to. 100,- 000 of the said mixture within the said zone.

10. The process of claim 8 wherein the said dehydrated stream of grease and additional lubricating oil are recycled continuously for at least about 5 passes through a shear valve with a pressure drop across the said valve of about 75-200 pounds per square inch.

11. The process of claim 1 wherein the temperature of the soap conditioning step is in the range of from about 350 to 370 F.

12. The process of claim 1 wherein the temperature of the soap conditioning step is in the range of from about 360 to 370 F.

References Cited UNITED STATES PATENTS 2,298,317 10/1942 Smith 25239 2,374,913 5/ 1945 Beerbower et a1 25239 2,383,906 8/ 1945 Zimmer et a1. -1.-- 25239 2,886,525 5/1959 Dilworth et a1. 25239 Roach et a1 25241 Crookshank et al 25241 Roach et a1 25239 Coons et al 252-41 McCormick et a1 252--41 Crookshank et al. 25241 Smith 25239 Calkins 252421 Beerbower 25239 Zimmer et a1. 25239 Ashburn et al 25241 Jones et a1 25239 X Nelson et al. 25241 Pitman et al 25239 X Dilworth et al. 25239 Hencke et al. 25241 Pelton et al. 252--39 DANIEL E. WYMAN, Primary Examiner 20 I. VAUGHN, Assistant Examiner UNITED suns PATENT omen CERTIFICATE OF CORRECTION mt no. 3.?5337 and October 28, 1969 unml. m, :r., Arnold c. we, .m, m rmw and Clarence L. Borden, Jr.

It in certified that error appears in tho above-identified patent and that aid Letter: hunt are hereby corrected 0 shown below:

00L 1, line 55, "linea' should read --t1nea--. GOLUII 6, line 65, '10" should read --70--.

Signed and sealed this 1st day of September 1970 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

